Treatment of metals



Patented Oct. 22, 1940 PATENT. OFFICE.

TREATMENT OF METALS Robert W. Shoemaker, Anderson, Ind., assignor to Agnes J. Reeves Greer, Morgantown, W. Va.

No Drawing. Application May 12, 1939, Serial No. 273,294

1 Claim. (Cl. 148-8) The invention relates to the treatment of metal, particularly to cleaning of metal articles as by pickling, and is more especially concerned with the pickling of coils of metal.

The common practice of pickling such articles is to immerse the articles in an acid solutionfor a sufiicient time to remove all oxidation from the surfaces, then rinse the articles in a bath of cold water for the purpose of removing some of the acid from the surfaces, and finally to rinse the articles in hot water in an effort to remove the remainder of the acid.

Metal treated in the above manner will quickly rust unless immediately subjected to some further treatment such as cold rolling, and even though the metal may be oiled after such a pickling and rinsing treatment where it is desired to store the same for some time before further treatment, it frequently happens that the metal rusts in a short time.

This is believed to be due to the fact that the pickling acid is not entirely rinsed from the metal by the cold and hot water baths, and that the metal is not quickly driedWhen removed from the hot water.

The object of the present invention is to provide a treatment which will entirely remove all traces of the pickling acid from the surfaces and pores of the metal and then quickly dry the metal and apply a thin film of oil to the surfaces so that the metal may be stored for some considerable time without danger of rusting.

In the treatment of coils of metal the invention may be carried out in a pickling machine such as disclosed in Greer Patent No. 2,091,921,-

wherein the coils are rotated as they are moved moved forward through the baths.

In carrying out the improved process for treatment of the coils, each coil is first passed through the pickling acid and then after time is allowed for the acid to drain therefrom, the coil is immersed in a bath of hot water, preferably slightly below theboiling temperature, a temperature of about 190 F., giving very satisfactory results in actual practice.

For the purpose of assisting in removing the pickling acid from the surface and pores of the metal a small amount of caustic alkali preferably, caustic soda may be dissolved in the hot water in this tank.

Satisfactory results have been obtained by using to lbs. of caustic soda in a bath of approximately 5700 gallons of hot water.

The coil is rotated upon its axis as it is passed through this hot water bath which removes the pickling acid from the surfaces of the metal much more efficiently than the cold water rinse.

When the coil is removed from the hot Water bath, it may be tilted slightly, as disclosed in said Greer patent, above referred to, in order to 5 quickly drain all of the water therefrom.

The coil is held in this position for a few seconds to permit the hot water to evaporate from the surfaces thereof; and in order to facilitate the evaporation of the water without materially 10 lowering the temperature of the metal, a blast of air, preferably hot air, may be directed upon the coil.

The coil when dried, but while still quite hot, is then immersed in a bath of hot water and oil 15 which may be maintained at a temperature apthereof, a thin film of oil will remain upon the surfaces of the metal.

There are many water soluble oils which may be used for this purpose and which are commercially obtainable from the large oil companies; an example of. a soluble oil which has given satisfactory results in carrying out the invention being composed of 20% soap, 78% N0. 1 straw parafiine oil, and 2% alcohol.

Where thecoils are to be stored for some considerable period of time before cold'rolling or otherwise processing, it has been found that the addition of a thin layer of an insoluble oil, such as a non-soluble light mineral, oil, to the surface of the hot water and soluble oil bath aids materially in protecting th surfaces of the metal against rust.

When the coil is lifted out of this bath it is coated with a thin film of hot water and soluble oil, and in passing up through the thin layer of insoluble mineral oil on the top of the bath this insoluble oil adheres readily to the oil coated surfaces of the metal.

Although the hot water rinse immediately following the pickling bath entirely cleans the su face of the metal there may be slight traces of the pickling acid remaining in the pores of the metal, and in order to entirely clean the pores to eliminate all traces of acid an alkali may be dis- 50 solved in the hot water.

For this purpose caustic soda has been found to be very satisfactory, and in carrying out the invention this alkali has been'used in the hot water and oil bath.

In actual practice the ingredients have been used in the proportions of about 5000 gallons of hot water to which is added about to gallons of soluble oil, such a commercial soluble oil as above mentioned, 50 to 150 lbs. of caustic soda, and 5 to 15 gallons of non-soluble light mineral oil, in cases where the bath is violently agitated during the operation. If the bath is not agitated in this manner then 50 to 150 gallons of mineral oil may be used forming a thin layer upon the top of the bath. 0

Where the smaller amount of mineral oil is used the continuous agitation of the bath while the metal is immersed therein, is for the purpose of assisting in displacing the water from the surfaces of the metal so that the oil may adhere thereto.

When the coil is removed from the hot water and oil bath it may again be tilted as disclosed therefrom, and the hot water may be quickly evaporated therefrom leaving the surfaces of the metal coated with a thin film of soluble and insoluble oil.

The drying of the coil at this stage may also be facilitated by directing a blast of air, preferably hot air, upon the coil.

It has been found in actual practice that coils of strip steel pickled and treated in the above manner will be entirely free from rust and may be stored for a considerable length of time without danger of rusting.

I claim:

The method of treating metal comprising pickling it, then immersing it in hot water and caustic alkali directly after said pickling, then quickly drying the metal, then immersing the metal in a bath of hot water and oil while it is still hot.

ROBERT W. SHOEMAKER. 20 

